Question

I’m using Prism with IoC. The problem is to pass an object (like collections) through navigation. I was watching this post: How to Pass an object when navigating to a new view in PRISM 4

And this is the solution

I extract the hash code of the object and save it in a Dictionary, with the hash code as the key and the object as the value of the pair.

Then, I attach the hash code to the UriQuery.

After, I only have to get the hash code that comes from the Uri on the target view and use it to request the original object from the Dictionary.

Some example code:

Parameter repository class:

public class Parameters
{
    private static Dictionary<int, object> paramList =
        new Dictionary<int, object>();

    public static void save(int hash, object value)
    {
        if (!paramList.ContainsKey(hash))
            paramList.Add(hash, value);
    }

    public static object request(int hash)
    {
        return ((KeyValuePair<int, object>)paramList.
                    Where(x => x.Key == hash).FirstOrDefault()).Value;
    }
}

The caller code:

UriQuery q = null;
Customer customer = new Customer();
q = new UriQuery();
Parameters.save(customer.GetHashCode(), customer);
q.Add("hash", customer.GetHashCode().ToString());

Uri viewUri = new Uri("MyView" + q.ToString(), UriKind.Relative);
regionManager.RequestNavigate(region, viewUri);

The target view code:

public partial class MyView : UserControl, INavigationAware
{
// some hidden code

    public void OnNavigatedTo(NavigationContext navigationContext)
    {
        int hash = int.Parse(navigationContext.Parameters["hash"]);
        Customer cust = (Customer)Parameters.request(hash);
    }
}

That’s it.

I’m not sure if this solution is the best to pass objects. I guess this maybe would be a service. Is a good way to do this or is there a better way to do it?

Answer 1

I posted an easier way. Mentioning it here for reference –

I would use the OnNavigatedTo and OnNavigatedFrom methods to pass on the objects using the NavigationContext.

First derive the viewmodel from INavigationAware interface –

 public class MyViewModel : INavigationAware
 { ...

You can then implement OnNavigatedFrom and set the object you want to pass as navigation context as follows –

void INavigationAware.OnNavigatedFrom(NavigationContext navigationContext)
{
     SharedData data = new SharedData();
     ...
     navigationContext.NavigationService.Region.Context = data;
}

and when you want to receive the data, add the following piece of code in the second view model –

void INavigationAware.OnNavigatedTo(NavigationContext navigationContext)
{
    if (navigationContext.NavigationService.Region.Context != null)
    {
        if (navigationContext.NavigationService.Region.Context is SharedData)
        {
             SharedData data = (SharedData)navigationContext.NavigationService.Region.Context;
              ...
        }
    }
}